INDEX , 491 



PAGE 



Stissing Mountain, fossils from 274 



stissingensis, see Micromitra (Paterina) . 

 stoneanus, see Obolus (JVestonia). 



Stones River formation, thin section of fossils from 151 



Strophomenacea, classification of 142 



defined 14S 



evolution of I45 



Strophomenidae, classification of 142, 148 



diagram showing line of descent 140 



distribution in Cambrian strata 140 



stuarti, st& Micromitra {Paterina). 

 stibcoronata, see Ptychoparia. 

 suhequata, see Dalmanella. 

 subquadrata, see Orthis. 

 subsidua, see Acrothele. 

 subsidua hera, see Acrothele. 

 sulcata, see Aero tret a idahoensis. 

 siiperba, see Micromitra (Paterina). 

 siipcrbus, see Neolenus. 



Swanton, fossils from 339 



thin sections of fossil from 151, 164 



Szvantonia, classification of 142, 148 



evolution of pi. 11 (pp. 140-141) 



Swantonia zveeksi, mentioned 300, 315 



stratigraphic position and association 189 



Szvantonia ? sp. undt., stratigraphic position and association 189 



Szvantonia ? , mentioned 300, 315 



Swasey formation, defined li 



House Range, correlated 171 



section of 181-182, pis. 16 and 17 



Syntrophia, classification of 142, 148 



compared vi^ith Clark ella iii 



Huenella 109, iii 



Polytoochia iii 



evolution of pi. 11 (pp. 140-141) 



mentioned 106 



Syntrophia barabiiensis, compared vi^ith Syntrophia nnxia ,. . 108 



Syntrophia calcifera, compared with Syntrophia cambria 107 



Syntrophia cambria, new species 106, pi. 10, figs. 11 and iia 



compared with Billingsella 107 



Syntrophia calcifera 107 



Syntrophia nundina 107 



stratigraphic position and association 196 



Syntrophia campbelli, new species 107, pi. 10, figs. 9, ga-c 



compared with Huenella texana 108 



Syntrophia rotundata 108 



Syntrophia lateralis, shell structure compared with that of Huenella ab- 



normis • 152 



thin section of 164, pi. 12, fig. 7 



